1. Field of the Invention
The present invention relates to a power supply device, and more particularly, to a power plug device capable of enhancing the quality of electrical power transmission.
2. Description of Prior Art
Electromagnetic Interference (EMI) or noise is caused by undesirable radiated electromagnetic fields or applied voltages and conducted currents. Interference is produced by a source emitter and is detected by a susceptible device via a coupling path involving the coupling mechanism of conduction—electric current. Conducted noise is coupled between components through interconnecting wires such as through power supply and ground wires. For example, common impedance coupling is caused when currents from two or more circuits flow through the same impedance such as in power supply and ground wires.
Such generated EMI has been known to interfere and affect the stability of electrical currents flowing through electric apparatus and appliances, and thus compromises device performance and shortens the usage life of the apparatus and appliances, sometimes resulting in such effects as partial overheating, insulation fatigue (break-down) over time, shortened lifespan, poor sound or image quality and so forth.
To assist with the above issues associated with unsteady electrical currents transmitted through electrical apparatus or appliances, Taiwan patent Publication 90127383, which is assigned to the applicant of this invention, has disclosed a power plug as shown in FIG. 1. As shown in the figure, the power plug 200 comprises: a terminal base 110 having a pair of conductive terminals 100 (hot and neutral) and a ground terminal 101, a cable 111 containing insulated wires respectively connected to the conductive terminals 100 and the ground terminal 101, a housing 120 connected with the terminal base 110, and a ground element 130 connecting a third conductor 27 to the ground. In that both the terminal base 110 and the housing 120 are made of insulative plastic material, the ground element 130 is adapted for grounding the third conductor 27 that is isolated from the power plug 200, shielding electromagnetic interference from affecting the power quality.
While the plastic terminal base 110 and the housing 120 are relatively inexpensive, they don't contribute much in terms of shielding against electromagnetic interference. Also, both the plastic terminal base 110 and the housing 120 have low structural rigidity and are prone to transmitting vibrations, thereby affecting electric power transmission and the usage life as a result. Also, it is necessary to employ an additional element for grounding in an attempt to shield against electromagnetic interference. As such, it is desirable and beneficial to provide a novel power plug that can improve on the drawbacks of prior techniques as described above.